A report from the Attorney General's office in Boston claims chemist Sonja Farak was also making crack cocaine in the Amherst lab.

"Obviously the conclusions, the findings of our report are disturbing, they're concerning, and it's why we undertook the thorough investigation that we did," Attorney General Maura Healey said.

Farak pleaded guilty in 2014 to a number of charges, including tampering with evidence and stealing drugs from the lab.

"Obviously, anytime the integrity of the criminal justice system is questioned, or there are allegations about concerns, we're going to take those seriously as we did in this instance, do our job, and report those to the court," Healey said.

But the new report could have a ripple effect on cases across Massachusetts.

"Potentially, this could affect many, many cases. What has to happen now is that the court is in receipt of this information, it's available for District Attorney's Offices and for defense counsel, and this will have to be evaluated in the context of each individual case," Healey said.

Investigators say Farak testified in court while under the influence of meth, ketamine, cocaine, LSD and other drugs.

The report says she got high almost every day at work for eight years and that she cooked crack cocaine in the drug lab after hours.

Farak admitted to stealing from evidence submitted by police departments for testing. She eventually started to manufacture her drugs at her workstation.

"She would enter the lab after hours or when she was working overtime, remove powdered cocaine from samples, and cook it to produce crack," according to the report.

The facility has since been closed.

“Her conduct has affected approximately 30,000 samples," said Anthony Benedetti, head of the state's public defenders. "We don’t know exactly how many individuals will be affected by that, but it’s safe to say in the tens of thousands.”

It's not clear how many cases could be affected. Farak handled at least 10,000 samples during her time at the lab.

“When you think about that, in terms of thousands of cases, it’s a lot of resources, it’s a lot of time, not just for us, but for the entire court system," said Benedetti. “If you are one of those individuals, and your case is potentially affected, you should not have to wait 3, 4, 5, 6 years in order to get before a judge and challenge your conviction.”

"We have provided the results of that investigation to the court, and the court will now move forward, determining how specific matters, cases may be handled that are currently pending before the court," Healey said.